1. Field of the Invention
The present invention relates to an improved high-pressure separation process for the manufacture of anhydrous lower alkyl alcohols by employing specifically chosen entrainers. More specifically, it pertains to a high-pressure azeotropic distillation process for producing a high-quality product of a C.sub.2 to C.sub.5 alkyl alcohol, e.g., isopropanol, and also regenerating a useable steam of sufficient pressures, e.g., 10 to 30 psig. by employing a high pressure steam of, e.g., 125 to 225 psig., and specially chosen entrainers, e.g., pentanes and cyclohexane.
2. Description of the Prior Art
Various cyclic and acyclic hydrocarbons such as cyclohexane, methylcyclohexane, cyclopentane, methyl cyclopentane, benzene, pentanes, hexanes, isopropyl ether, ethyl ether and the like have been suggested as entraining agents for the purification of lower alkanols via azeotropic distillation. For example, U.S. Pat. No. 3,239,435 (Conseiller et al.; 1966) discloses that mixtures of aqueous alcohols can be separated under atmospheric pressure by employing cyclohexane as the entrainer. Benzene has also been widely utilized particularly in low-pressure, e.g., 0-40 psig., separation systems of lower alkanols.
With the soaring energy cost and expanding awareness of potential deleterious effects of various chemicals in human bodies and environments, today's chemical industry, including the manufacturing industry of lower alcohols, is faced with tremendous ecological, toxicological and economical challenges. Conventional methods of producing anhydrous alcohols such as the ones discussed above, however, are inadequately designed to meet the socioeconomic challenges. The common low-pressure azeotropic distillation operations are less economic due to their large consumption of energy; and, furthermore, the use of benzene has recently aroused greater concern due to its potential safety and carcinogenic hazards. Accordingly, the need has existed for an effective commercial process for manufacturing high-quality lower alcohols, which enjoy a wide variety of commercial applications such as solvents for surface coatings and printing inks, and bactericidal agents in pharmaceutical, cosmetic and toiletry products, at a lower manufacturing cost and without creating potential safety and health problems.